A fuel cell is a device for converting the chemical energy of a fuel directly into electrical energy in a continuous process. Although, in principle the nature of the reactants is not limited, the fuel cell reaction almost always involves the combination of hydrogen in some form with oxygen. Consequently, hydrogen generation and storage is a requirement for the pervasive introduction of fuel cells into the marketplace. To date, many options have been utilized for the hydrogen source of an H2/O2 fuel cell. Among the more common hydrogen storage materials are LiAlH4 and LiBH4. The reaction of lithium amide with water is also used for low temperature generation of hydrogen. Typical practical storage densities are on the order of 10% by mass of material, not considering system issues such as valving. Other types of hydrogen storage materials include methane, which can store up to 25% hydrogen by mass but being a gas requires storage means that can drive up system mass and volume. Methanol is an attractive choice based on cost and availability; however, hydrogen comprises only 12% by mass and, additionally, a high temperature reformer is required to access the hydrogen, driving up system volume and mass. Moreover, the reforming process produces CO and CO2 that can poison the catalysts on the proton exchange membrane. Alanates can be attractive sources as well but require water to activate, are hazardous and, in some cases, form oxides upon reaction with water that inhibit further reaction from occurring.
In an attempt to overcome the problems associated with an H2/O2 fuel cell, attention has been drawn to the use of direct injection of beta particles into a p/n junction to generate electricity (cf. U.S. Pat. Nos. 5,606,213, Nuclear batteries; 6,774,531, Apparatus and method for generating electrical current from the decay process of a radioactive material; 5,721,462, Nuclear battery and 3,934,162, Miniaturized nuclear battery). However, conversion efficiencies for this process rarely exceed 1%, the reported lifetimes are very limited and these devices are capable of only producing very limited power.